This invention relates to an assembly for collecting a liquid sample from a patient, such as a blood sample. More particularly, this invention relates to a needle assembly for collecting either a single or a multiple liquid sample from such a patient. The device of the invention utilizes a receiving chamber with walls which are translucent or transparent for visually indicating whether or not proper access to the sample in question has been achieved. Moreover, the chamber incorporates therein a reciprocal porous plug which plug is comprised of material which provides simultaneously a liquid barrier for the sample received, and a gas displacement discharge passage for gas displaced by the liquid sample received in the chamber.
The plug reciprocates in the chamber as required to first receive the liquid sample in question, while sealing the chamber against discharge of the sample, and simultaneously venting gas displaced by the liquid sample. Subsequently, when the liquid sample is to be discharged to either a single vacuum collection device or a plurality of them, the plug reciprocates to cooperate with certain vents in the discharge area of the assembly for allowing passage of the collected sample to discharge sequentially to one or more vacuum collection devices. In those instances where multiple samples are to be collected and sequentially discharged to a plurality of vacuum collection devices, the assembly incorporates a flexible sleeve which cooperates with the discharge opening of the device during periods of exchange of the vacuum collection devices for a subsequent discharge of an additional sample.
As discussed above, it is desirable to provide a mechanism whereby the user of such a needle assembly can be informed when the intravenous needle has penetrated the vein of the patient for collection of a blood sample. Many times in collecting blood from a patient it is difficult to locate the vein, or for other reasons blood flow into the collecting device is not adequate. In those instances, it is advantageous to be able to make a quick determination that entry into the vein has been made and that blood is flowing into the needle assembly. Once this determination has been made and the vein entry achieved, the evacuated blood collection container can be inserted into the collection assembly in accordance with well known techniques of collecting blood samples during a single collection procedure.
One of the problems which arise during the venipuncture step concerns the pockets of air which are found in various needle assemblies for either single or multiple sample blood collections. When venipuncture is made, and the evacuated blood collection container is not yet attached to the opposite end of the needle structure, blood cannot always flow into the needle assembly because of a pocket of air which, under normal atmospheric conditions, remains inside the needle assembly. Thus, even though vein entry may have been accomplished, blood flow may not have begun, simply because of the air pocket blockage in the assembly.
With this invention, by contrast, through the utilization of a porous vent plug in the collection chamber, the plug allows for displacement of the air from the collection chamber so as to allow room for receiving the blood sample being collected. Moreover, the plug is so arranged to be reciprocable in the chamber to cooperate with vents in a discharge negative pressure cannula in the assembly for first venting the displaced air during the receiving portion of the procedure for receiving the sample, and subsequently discharging the sample to the vacuum blood collection container when such a container is attached to the assembly. For example, in one embodiment of the invention, for a single sample collection procedure, the assembly of the invention includes a porous plug which vents the displaced air when the sample is received, and then moves in response to a pressure differential to open passages in the assembly to discharge the sample received into an evacuated blood collection container, when such container is attached to the assembly and the discharge negative pressure cannula penetrates into the vacuum of an evacuated collection container.
Another embodiment of the invention includes a flexible sleeve covering the discharge opening of the negative pressure cannula. The flexible sleeve is so arranged to allow discharge from a third air discharge vent in the discharge cannula during the sample receiving procedure. Subsequently, the flexible sleeve is flexed and moved to cover this discharge opening when an evacuated blood collection container is inserted into the assembly for penetration by the negative pressure cannula. Once a single sample has been obtained in the evacuated blood collection container, and the container removed from the assembly, the flexible sleeve again covers the discharge opening in the negative pressure cannula until such time as subsequently, an additional evacuated blood collection container is attached for a subsequent collection of a second sample. As will be obvious to practitioners-in-the-art, this procedure may be repeated for collecting the number of samples required in individual evacuated blood collection containers.
In considering the utilization of a porous plug in blood collection assemblies of the kind described herein, in a previously filed patent application entitled "Blood Sampling Assembly Having Vein Entry Indicator" by William N. Eldridge, U.S. Ser. No. 915,670 filed June 15, 1978, now U.S. Pat. No. 4,207,870 issued June 17, 1980 and assigned to the common assignee herewith, the inventor recognized that this air blockage problem prevented the blood from flowing as desired through the intravenous needle to a point where it could be seen by a user. In the Eldridge invention, a porous vent means is provided in combination with a one-way valve whereby air inside the needle assembly is allowed to pass out of this venting means during the initial stages of the blood collection procedure. The venting means prevents the passage of blood until the user attaches the evacuated blood collection container to the needle assembly. Once the negative pressure of the evacuated blood collection container is attached, a separate one-way valve opens and allows blood to travel from the vein of the patient, and through the needle assembly and on into the container.
Although the Eldridge invention recognizes the utilization of a porous material for providing a venting for displaced air during receiving a blood sample, there is still room for improvement over such a device and particularly with respect to the present invention wherein the plug is a reciprocal plug which operates not only as a vent, but also as a valve structure in and of itself with no separate complicated structure for use in providing the valving action. Thus, the plug of the invention herein sealingly engages in reciprocal cooperation with the blood receiving chamber for simultaneously blocking discharge of the blood sample while venting displaced air from the receiving chamber and subsequently reciprocating to allow discharge of the received sample at the moment when the assembly is attached to an evacuated blood collection container.
Other related applications include U.S. patent application Ser. No. 160,781 filed June 18, 1980, now U.S. Pat. No. 4,340,068 issued July 20, 1982 and co-pending U.S. patent application Ser. No. 284,894, filed July 20, 1981 entitled "Multiple Sample Needle Assembly With Vein Entry Indicator".
Other objects and advantages of this invention will be apparent from the following description, the accompanying drawings and the appended claims.